摘要
为了研究混凝土中孔隙液pH值下降时钢筋热镀锌层的腐蚀,模拟了不同pH值(9.0～13.5)饱和Ca(OH)2溶液的混凝土孔隙液,将热镀锌钢筋浸泡15d,探讨了其在6种不同pH值溶液中的腐蚀行为和热镀锌层表面腐蚀产物。采用电化学测试、SEM、EDS和XRD技术对热镀锌钢筋进行了分析。结果表明:当pH值为9.0～12.0时,锌层表面主要生成ZnO膜,自腐蚀电流密度Jcorr随pH值增大而增大;当pH值为12.0～13.0时,锌层表面生成片状的锌酸钙,Jcorr明显减小;2种情况下Jcorr均接近钢筋钝化临界值0.1μA/cm2,锌层同样可处于钝化状态;当pH值为13.5时,锌层表面不生成保护膜,Jcorr显著增大到1×102μA/cm2。
Six kinds of saturated Ca(OH)2 solutions with different pH values were prepared as simulated concrete pore solutions. The hot-dip galvanized steel reinforcing bars immersed for 15 d in the resulting simulated solutions with varied pH values were evaluated by conducting electrochemical test and using a scanning electron microscope,an energy dispersive spectrometry and an X-ray diffractometer. It was found that when immersed in the saturated Ca(OH)2 solutions with a pH value of 9.0~12.0,the surface of the hot-dip galvanized steel was mainly covered with ZnO coating,and the corrosion current increased with increasing pH value. When immersed in the simulated Ca(OH)2 solutions with a pH value of 12.0~13.0,sheet-like calcium hydroxyzincate (CaHZn) was formed on the surface of the hot-dip galvanized steel,and the corrosion current decreased sharply with increasing pH value. Within a pH value range of 9.0~13.0,the corrosion current density was close to 0.1 μA/cm2,which was the critical current density for passivation of the steel reinforcing bars,and it indicated that the hot-dip galvanized steel was passivated while immersed in the saturated Ca(OH)2 solutions with a pH value of 9.0~13.0. Moreover,when immersed in the saturated Ca(OH)2 solution with a pH value of 13.5,no protective coating was formed on the surface of the hot-dip galvanized steel,at which the corrosion current drastically increased to 100 μA/cm2.
出处
《材料保护》
CAS
CSCD
北大核心
2010年第5期13-16,共4页
Materials Protection
关键词
腐蚀
热浸镀锌
混凝土钢筋
corrosion
hot-dip galvanizing
concrete steel reinforcing bar
